The present invention relates generally to electrical communications, and more particularly to signal processing methods.
High-resolution processing techniques do not always produce significant amounts of gain in the signal-to-noise ratio (SNR) of input underwater acoustic signal and noise data. Further SNR gain improvements normally require an additional technique specifically designed to produce high gain. A signal processing method that simultaneously improves both resolution and SNR gain would be particularly useful for underwater applications that benefit from both resolution and gain improvements.
In the case of underwater acoustics, natural fluctuations in the signal and the noise across time are caused by many factors, including multipath transmission, internal waves, acoustic propagation path interaction with the moving sea surface, and source-receiver relative motion. The advanced WISPR (Wagstaff's Integration Silencing Processor) summation (AWSUM) filter disclosed in Application Ser. No. 08/314,281, filed Sep. 30, 1994, by Wagstaff as sole inventor, and currently pending, the disclosure of which is hereby incorporated by reference, is a signal processing algorithm that has been found to increase the SNR for low-fluctuation amplitude tonal (LOFAT) signals embedded in high-fluctuation amplitude tonal (HIFAT) signals and noise by attenuating the highly fluctuating components more than the LOFAT signals. LOFAT signals are an important class of man-made signals in the ocean, and the AWSUM filter can provide significant gains for automatically detecting and classifying those signals (e.g. projector at the surface or submerged).